CN114478923A - High-toughness anti-freezing conductive hydrogel and preparation method thereof - Google Patents

Abstract

The invention relates to a preparation method of hydrogel, in particular to high-toughness anti-freezing conductive hydrogel and a preparation method thereof, belonging to the field of polymer preparation. The hydrogel is obtained by taking polyvinyl alcohol, acrylamide, N-vinyl pyrrolidone, sodium alginate and glycerol monomers as raw materials, borax as a cross-linking agent of the polyvinyl alcohol, N-methylene bisacrylamide as a cross-linking agent of the acrylamide and potassium persulfate as an initiator through a free radical reaction, and then carrying out post-treatment through a drying-swelling method to obtain a final product. The hydrogel prepared by the invention has higher toughness and antifreezing property, and the cost of the selected raw materials is lower, so that the hydrogel has wide market prospect. Simple steps, convenient operation and strong practicability.

Description

A kind of high toughness, antifreeze conductive hydrogel and preparation method

technical field

The invention relates to a preparation method of a hydrogel, in particular to a preparation method of a high-toughness, antifreeze conductive hydrogel, and belongs to the field of polymer preparation.

Background technique

The disclosure of information in this Background section is only for enhancement of understanding of the general background of the invention and should not necessarily be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art.

Hydrogel is a kind of polymer material with a three-dimensional cross-linked network structure and a large amount of water inside. In the gel network, the water molecules are closely combined with the hydrophilic groups of the polymer chains, and the liquid is difficult to process under normal temperature and pressure, and it is transformed into a solid-like state with limited mobility. Therefore, hydrogel materials have both good solid mechanical properties and fluid thermodynamic properties of traditional bulk materials. As a soft material with water as the main component, hydrogel has strong plasticity, good elasticity and biocompatibility, and has great application prospects in the fields of soft robots, intelligent actuators, tissue engineering and flexible electronic devices.

Flexible electronics with remarkable electrical conductivity and sensing capabilities similar to human skin are of great interest in advancing human epidermis detection, implantable sensors, and real-time monitoring sensors. In general, these devices should have suitable mechanical toughness, elastic modulus that matches that of the human body, and high sensitivity to efficiently convert physiological parameters into detectable electrical signals. Among different types of sensing materials, hydrogel, as an extremely hydrophilic three-dimensional network structure gel, deformable and ductile conductive hydrogel is one of the most suitable sensor candidates. It has a tunable biocompatible elastic modulus with on-demand engineered mechanical properties covering all moduli of human tissue for sensing applications.

However, conventional hydrogels usually use water as the electron-ion medium. Although electrical and mechanical properties are obtained, most of the composite hydrogels cannot withstand extreme environments and are not environmentally stable. It dries out at high temperatures and freezes at sub-zero temperatures. Even at room temperature, hydrogels inevitably lose water, resulting in weak mechanical hardening and deformability, hindering the environmental stability and operational durability of executable electrical devices. Ionically conducting hydrogels are particularly attractive due to their simple preparation process, low cost, and high electrical conductivity. However, although the abundant water in ionic hydrogels can provide desirable electrical conductivity and efficient ion transport, it usually leads to mechanical strength. However, the poor freezing resistance of ionically conductive hydrogels limits its application in extreme cold environments. This is because the large amount of water in the hydrogel inevitably freezes at subzero temperatures, which affects the mechanical elasticity and ion transport ability of the hydrogel.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the defects in the existing materials, and to provide a high toughness, antifreeze conductive hydrogel and a preparation method.

For realizing the above-mentioned technical purpose, the present invention adopts following technical scheme:

A first aspect of the present invention provides a method for preparing a high-toughness, antifreeze conductive hydrogel, comprising:

Add polyvinyl alcohol, acrylamide, N-vinyl pyrrolidone, acrylamide cross-linking agent, polyvinyl alcohol cross-linking agent, and initiator to the sodium alginate solution and mix uniformly, and heat for copolymerization to obtain a hydrogel;

The hydrogel is subjected to drying-swelling treatment, that is, it is obtained.

Sodium alginate (SA), a natural and inexpensive polysaccharide composed of two substituted units α-Lguuronic acid and P-D-mannonic acid, has attracted much attention due to its good biocompatibility and biodegradability. It has a wide range of applications in the fields of chemistry, biology, medicine and food. In addition to good biocompatibility, sodium alginate can also act as a polyelectrolyte, giving the hydrogels good electrical conductivity. In addition, sodium alginate can also improve the mechanical strength in the hydrogel system. Traditional acrylamide hydrogels tend to have low strength, so we introduced N-vinylpyrrolidone into the system to form a copolymerization system with acrylamide to enhance the strength of the hydrogel. At the same time, we also induced the formation of PVA crystallites in the composite hydrogel by a drying-swelling method, which can effectively improve the mechanical properties of the hydrogel.

The study found that glycerol, as an organic solvent, can form strong hydrogen bonds with water molecules, thereby destroying the ice lattice at sub-zero temperatures to achieve antifreeze effect and prevent water from evaporating. In addition, one glycerol molecule can provide three hydroxyl groups; therefore, glycerol can also act as a cross-linking agent for polyvinyl alcohol chains, thereby improving the strength and toughness of polyvinyl alcohol hydrogels. Polyvinyl alcohol can form borate bond with borax solution to give the system a good self-healing effect. At the same time, the abundant hydroxyl groups on the polyvinyl alcohol chain can form dense hydrogen bonds with polyacrylamide and sodium alginate to endow the hydrogel with excellent toughness.

The second aspect of the present invention provides the high toughness, antifreeze conductive hydrogel prepared by the above method.

The third aspect of the present invention provides the application of the hydrogel in the manufacture of soft robots, intelligent actuators, tissue engineering and flexible electronic devices.

The beneficial effects of the present invention are:

(1) The preparation process of the present invention makes full use of the viscous characteristics of sodium alginate, and the conductive hydrogel mixed with sodium alginate has better mechanical strength and better electrical conductivity at the same time.

(2) The introduction of glycerin can not only form a strong hydrogen bond with water molecules, destroy the ice lattice under zero degrees to achieve antifreeze effect, but also improve the mechanical strength of the hydrogel as a crosslinking agent of polyvinyl alcohol chain.

(3) Further treatment of the hydrogel by the drying-swelling method can induce the crystallization of PVA to improve the mechanical properties and stability of the hydrogel.

(4) The preparation method of the present invention is simple, low in price, strong in practicability, and easy to popularize

Description of drawings

The accompanying drawings forming a part of the present invention are used to provide further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute an improper limitation of the present invention.

Figure 1 is a stress-strain diagram of the hydrogels prepared in each example, wherein 5%-9% represents the content of sodium alginate in the system.

Figure 2 shows the stress-strain diagrams of hydrogels with different glycerol content, where 0%-30% represents the content of glycerol in the system.

Figure 3 is a graph showing the toughness of hydrogels with different glycerol contents.

Figure 4 is the DSC curves of hydrogels with different glycerol content.

Figure 5 shows the electrical signal of the conductive hydrogel as a strain sensor.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

A high-toughness, antifreeze conductive hydrogel and a preparation method, comprising: preparing a composite hydrogel in a polyvinyl alcohol, acrylamide and N-vinylpyrrolidone hydrogel system added with sodium alginate and glycerin in different proportions. A drying-swelling treatment is then performed to obtain the final product. In the system, the addition amount of sodium alginate is 5%-9%, and the addition amount of glycerol is 0%-30%.

In some embodiments, sodium alginate is dissolved in water with heating and stirring, followed by cooling to room temperature. Add polyvinyl alcohol, acrylamide, N-vinylpyrrolidone, potassium persulfate, N,N-methylenebisacrylamide and borax to the above solution, and place it in a water bath at 50-80°C for heating. N-vinylpyrrolidone was copolymerized to obtain a hydrogel. The prepared hydrogel was then completely dried and soaked in water to re-swell to obtain the final product.

In some embodiments, after selecting the optimal addition amount of sodium alginate in the above hydrogel, glycerol is added to the hydrogel system.

The present invention will be further described in detail below with reference to specific embodiments. It should be pointed out that the specific embodiments are intended to explain rather than limit the present invention.

Example 1:

Dissolve sodium alginate with a mass content of 5% in a certain amount of water and heat it at 90° C. until fully dissolved. After cooling to room temperature, 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N,N-methylenebisacrylamide, 0.04g potassium persulfate and 5g 0.6wt% borax solution Add the above solution. After fully stirring for one hour, it was placed in a 60°C water bath and heated for 4-6 hours to obtain a hydrogel. The prepared hydrogel was placed in an oven at 50-60 °C to be completely dried, and then the dried gel was soaked in water for 2 h to re-swell to obtain the final product.

Example 2:

Dissolve sodium alginate with a mass content of 6% in a certain amount of water and heat it at 90° C. until fully dissolved. After cooling to room temperature, 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N,N-methylenebisacrylamide, 0.04g potassium persulfate and 5g 0.6wt% borax solution Add the above solution. After fully stirring for one hour, it was placed in a 60°C water bath and heated for 4-6 hours to obtain a hydrogel. The prepared hydrogel was placed in an oven at 50-60 °C to be completely dried, and then the dried gel was soaked in water for 2 h to re-swell to obtain the final product.

Example 3: Dissolve sodium alginate with a mass content of 7% in a certain amount of water and heat it at 90° C. until fully dissolved. After cooling to room temperature, 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N,N-methylenebisacrylamide, 0.04g potassium persulfate and 5g 0.6wt% borax solution Add the above solution. After fully stirring for one hour, it was placed in a 60°C water bath and heated for 4-6 hours to obtain a hydrogel. The prepared hydrogel was placed in an oven at 50-60 °C to be completely dried, and then the dried gel was soaked in water for 2 h to re-swell to obtain the final product.

Example 4: Dissolve sodium alginate with a mass content of 8% in a certain amount of water and heat at 90° C. until fully dissolved. After cooling to room temperature, 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N,N-methylenebisacrylamide, 0.04g potassium persulfate and 5g 0.6wt% borax solution Add the above solution. After fully stirring for one hour, it was placed in a 60°C water bath and heated for 4-6 hours to obtain a hydrogel. The prepared hydrogel was placed in an oven at 50-60 °C to be completely dried, and then the dried gel was soaked in water for 2 h to re-swell to obtain the final product.

Example 5: Dissolve sodium alginate with a mass content of 9% in a certain amount of water and heat it at 90° C. until fully dissolved. After cooling to room temperature, 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N,N-methylenebisacrylamide, 0.04g potassium persulfate and 5g 0.6wt% borax solution Add the above solution. After fully stirring for one hour, it was placed in a 60°C water bath and heated for 4-6 hours to obtain a hydrogel. The prepared hydrogel was placed in an oven at 50-60 °C to be completely dried, and then the dried gel was soaked in water for 2 h to re-swell to obtain the final product.

Example 6: As shown in Figure 1, we can see from the stress-strain diagram that the hydrogel has a good mechanical property when the content of sodium alginate is 5%. Therefore, this ratio was chosen for the following experiments. Dissolve sodium alginate with a mass content of 7% in a certain amount of water and heat it at 90° C. until fully dissolved. After cooling to room temperature, 16g of polyvinyl alcohol, 4g of acrylamide, 2g of N-vinylpyrrolidone, 0.01g of N,N-methylenebisacrylamide, 0.04g of potassium persulfate, 5g of borax solution with a concentration of 0.6wt% were mixed And 5% content of glycerol was added to the above solution. After fully stirring for one hour, it is placed in water at 60°C and heated for 4-6 hours to obtain a hydrogel. The prepared hydrogel was placed in an oven at 50-60 °C to be completely dried, and then the dried gel was soaked in water for 2 h to re-swell to obtain the final product.

Example 7: Dissolve sodium alginate with a mass content of 7% in a certain amount of water and heat it at 90° C. until fully dissolved. After cooling to room temperature, 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N,N-methylenebisacrylamide, 0.04g potassium persulfate, 5g 0.6wt% borax solution And 5% mass content of glycerol was added to the above solution. After fully stirring for one hour, it was placed in a 60°C water bath and heated for 4-6 hours to obtain a hydrogel. The prepared hydrogel was placed in an oven at 50-60 °C to be completely dried, and then the dried gel was soaked in water for 2 h to re-swell to obtain the final product.

Example 8: Dissolve sodium alginate with a mass content of 7% in a certain amount of water and heat it at 90° C. until fully dissolved. After cooling to room temperature, 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N,N-methylenebisacrylamide, 0.04g potassium persulfate, 5g 0.6wt% borax solution And 10% mass content of glycerol was added to the above solution. After fully stirring for one hour, it was placed in a 60°C water bath and heated for 4-6 hours to obtain a hydrogel. The prepared hydrogel was placed in an oven at 50-60 °C to be completely dried, and then the dried gel was soaked in water for 2 h to re-swell to obtain the final product.

Example 9: Dissolve sodium alginate with a mass content of 7% in a certain amount of water and heat at 90° C. until fully dissolved. After cooling to room temperature, 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N,N-methylenebisacrylamide, 0.04g potassium persulfate, 5g 0.6wt% borax solution And 20% mass content of glycerol was added to the above solution. After fully stirring for one hour, it was placed in a 60°C water bath and heated for 4-6 hours to obtain a hydrogel. The prepared hydrogel was placed in an oven at 50-60 °C to be completely dried, and then the dried gel was soaked in water for 2 h to re-swell to obtain the final product.

Example 10: Dissolve sodium alginate with a mass content of 7% in a certain amount of water and heat it at 90° C. until fully dissolved. After cooling to room temperature, 16g of polyvinyl alcohol, 4g of acrylamide, 2g of N-vinylpyrrolidone, 0.01g of N,N-methylenebisacrylamide, 0.04g of potassium persulfate, 5g of 0.6wt% borax solution and 30% mass content of glycerol was added to the above solution. After fully stirring for one hour, it was placed in a 60°C water bath and heated for 4-6 hours to obtain a hydrogel. The prepared hydrogel was placed in an oven at 50-60 °C to be completely dried, and then the dried gel was soaked in water for 2 h to re-swell to obtain the final product.

Comparative Example 1:

Mix 16g of polyvinyl alcohol, 4g of acrylamide, 2g of N-vinylpyrrolidone, 0.01g of N,N-methylenebisacrylamide, 0.04g of potassium persulfate, 5g of borax solution with a concentration of 0.6wt%, and stir well for one hour Then, the hydrogel was obtained by heating in a water bath at 60°C for 4-5 hours. The prepared hydrogel was placed in an oven at 50-60 °C to be completely dried, and then the dried gel was soaked in water for 2 h to re-swell to obtain the final product.

Comparative Example 2:

Dissolve sodium alginate with a mass content of 7% in a certain amount of water and heat it at 90° C. until fully dissolved. After cooling to room temperature, 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N,N-methylenebisacrylamide, 0.04g potassium persulfate, 5g 0.6wt% borax solution Add the above solution. After fully stirring for one hour, it was placed in a 60°C water bath and heated for 4-6 hours to obtain a hydrogel. The prepared hydrogel was placed in an oven at 50-60° C. to be completely dried, and then the dried gel was soaked in water for 2-4 hours to re-swell to obtain the final product.

As shown in FIG. 2 and FIG. 3 , the stress-strain curve diagrams and the toughness diagrams of the corresponding proportions of the hydrogels obtained in the examples are shown. It can be seen that with the increase of glycerol content, the stress and strain show a trend of increasing first and then decreasing. At the same time, it can be seen that the toughness of the hydrogel reaches the maximum when the glycerol content is 10%.

As shown in Figure 4, with the increase of glycerol content, the freezing point of the hydrogel gradually decreased and all have good antifreeze effect, and different proportions of glycerol can be selected according to the needs of different applications.

As shown in Figure 5, the hydrogel can transmit a good electrical signal as a strain sensor.

Finally, it should be noted that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, the Modifications may be made to the technical solutions described in the foregoing embodiments, or equivalent replacements may be made to some of them. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A preparation method of a high-toughness anti-freezing conductive hydrogel is characterized by comprising the following steps:

adding polyvinyl alcohol, acrylamide, N-vinyl pyrrolidone, a crosslinking agent of acrylamide, a crosslinking agent of polyvinyl alcohol and an initiator into a sodium alginate solution in sequence, uniformly mixing, and heating for copolymerization to obtain hydrogel;

and drying and swelling the hydrogel to obtain the hydrogel.

2. The method for preparing the high-toughness anti-freezing conductive hydrogel according to claim 1, wherein the content of the sodium alginate is 5% -9%.

3. The method for preparing the high-toughness anti-freezing conductive hydrogel according to claim 1, wherein the copolymerization reaction is carried out at 50-80 ℃ for 4-6 hours.

4. The method for preparing the high-toughness anti-freezing conductive hydrogel according to claim 1, wherein the cross-linking agent of the polyvinyl alcohol is borax and glycerol.

5. The method for preparing the high-toughness anti-freezing conductive hydrogel according to claim 1, wherein the cross-linking agent of acrylamide is N, N-methylene bisacrylamide.

6. The method for preparing a high-toughness, anti-freezing, electrically-conductive hydrogel according to claim 1, wherein said initiator is potassium persulfate.

7. The method for preparing the high-toughness antifreeze conductive hydrogel according to claim 1, wherein the drying temperature in the drying-swelling treatment is 50 to 60 ℃.

8. The method for preparing the high-toughness anti-freezing conductive hydrogel according to claim 1, wherein the swelling time is 2-4 h.

9. A high-toughness, freeze-protected, electrically conductive hydrogel prepared by the method of claims 1-8.

10. Use of the hydrogel of claim 9 in the manufacture of soft-bodied robots, smart actuators, tissue engineering and flexible electronics.

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